This invention relates to a dual brush cleaning apparatus, and more particularly to an apparatus for removing residual material from the surface of an electrostatographic imaging member. An electrostatographic reproducing machine employing the apparatus also forms part of this invention.
The use of dual brushes in a cleaning apparatus for removing residual material from the surface of an electrostatographic imaging member is known as shown, for example, in U.S. Pat. Nos. 3,062,178 to Huber; 3,062,956 to Codichini; and U.S. Pat. No. 3,795,025 to Sadamitsu.
Other cleaning systems have been proposed wherein more than one cleaning device is provided in order to have redundancy in the cleaning system. For example, U.S. Pat. No. 3,552,850 to Royka et al. discloses the use of multiple cleaning blades. In U.S. Pat. No. 3,859,691, to Katayama, a cleaning blade followed by a fabric roller is disclosed as an alternative to multiple blades. In U.S. Pat. No. 3,807,853 the use of multiple foam cleaning rolls is described.
In U.S. Pat. No. 3,741,157 to Krause, an air jet cleaning apparatus followed by a brush cleaner is described. It is noted in this patent that brush cleaning can result in filming of the photoconductor surface and other damage due to the continuous contact between the brush and the surface. Therefore, the combination of air jet cleaning and brush cleaning leads to an increase in the usable life of the photoconductor surface. It is pointed out that the air jet cleaning system does the main cleaning so the brush fibers do not have to transport as much toner as in a conventional brush cleaning system and, therefore, the brush can be rotated at a much slower speed than a conventional brush. The slower speed of the brush reduces local heating and deformation of the photoconductive surface so that there is a corresponding increase in the useful life of this member as compared to systems utilizing only brush cleaning.
It has been found in accordance with this invention that photoconductor filming due to brush cleaning is attributable at least in part to the build-up of residual toner in the cleaning brush. The brush becomes impacted with toner which then impacts on the photoconductor surface. Therefore, in accordance with this invention a means has been devised for reducing the build-up of residual toner in the brushes. In prior art, dual brush cleaning systems the brushes were normally operated at a brush to imaging surface interference which was the same for both brushes. The net result of this approach is that the first of the two brushes performs cleaning as if it were the only brush. The second brush in the direction of photoconductor travel cleans any residue which passes the first brush. This does not substantially reduce toner build-up in the first brush and it is likely to cause drum filming and poor cleaning at the same rate as a single brush.